<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<style>
    .root{
        display: flex;
        padding:24px 0 0 24px;
        width: 1000px;
        background-color: pink;
    }
    .item1{
        flex: 1;
    }
</style>




<body>
 <div class="root">
        <div class="item1">aa</div>
        <div>bb</div>
 </div>
</body>
</html>